Cellular supporting materials such as microcarriers have been used for growing cultured cells in vitro. Cultured cells can be harvested from the cellular supporting materials, for example, by using proteolytic enzymes. Once the cells are separated from the cellular supporting materials, the issue remains to separate the cellular supporting materials from the now free-floating cells. It is therefore desirable to have a differential filtration process whereby the used cellular supporting materials may be separated from the cells that were formerly adhered to the surface of the cellular supporting materials.